To achieve excellent image quality and highly defined contrast in a liquid color display, a black matrix having high-shielding performance must be formed among pixels of three colors in a color filter. In a liquid color display having an active matrix drive system and employing a thin film transistor, good shielding performance is required. Good shielding, in particular, prevents the deterioration in image quality which accompanies current leakage due to the light emitted by the thin film transistor.
Black matrices have generally been prepared by depositing a chrome film on a substrate, for example, by sputtering, and patterning the chrome film by photolithography. Although this method using chrome can provide a black matrix having high accuracy and good shielding performance due to the thin film, it is disadvantageous in some respects. Namely, the vacuum film-forming process (e.g., chrome sputtering) that is required in this method increases the cost. Moreover, the waste liquid from the process of chrome etching presents a safety problem.
On the other hand, there is another method for forming a black matrix without using chrome. This method comprises dispersing a black pigment (e.g., carbon black) and a dye in a resist followed by photographic patterning. Although this method can improve safety and reduce cost as compared with using chrome, the resist containing a black dye or pigment fails to achieve sufficient resolution. In the case of thick black matrix pixels (about 1 .mu.m thick), other pixels formed by the resist method, etc. would partly overlap the black matrix pixels, thus causing unevenness in thickness. As a result, the liquid panel (i.e., the final product) suffers from cell gap irregularities which create problems in the display (color shading, etc.). Therefore, the film thickness of the black matrix pixel is desirably about 0.7 .mu.m or less. However, it is difficult to establish sufficient shielding performance in this thickness range employing this method.
A method using electroless deposition as disclosed in JP-A-6-75110, etc. (the term "JP-A" as used herein means an "unexamined published Japanese patent application") can provide a black matrix having a satisfactory shielding performance even at a thickness of 0.7 .mu.m or less. This is because a metal is deposited in the electroless deposition. However, another disadvantage arises in that the thin film has a high reflectance. This makes the panel face dazzling to thereby deteriorate contrast.
In the method described in JP-A-4-32802 using reduction of a silver salt, a silver halide emulsion is applied onto a substrate. After exposure via a mask, the black matrix part thus irradiated is developed and fixed to thereby reduce and deposit the silver. Although this method is relatively inexpensive, the emulsion layer remains not only in the black matrix but also in other parts of the color filter. This frequently causes coloration in the heating process for paneling, or wrinkling or cracking after the formation of a transparent electrode.